I am glad that this situation worked out for you....
I personally cannot take in anyone who is NOT okay with me transporting when necessary.I have older kids, and sometimes we have to leave the house. I offer the use of my carseats, but will use theirs if they are more comfortable. I have extra liability insurance on my vehicle, and have them sign a transport waiver. But all of this is discussed up front. I can understand why someone may feel upset if it wasn't talked about. Although it sounds like they aren't reading the notices, etc and that is not your fault!